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Bic - Evolution Triangle - Triangular Pencils with Integrated Eraser - HB - Box of 12

£11.25£22.50Clearance
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Zumdahl, Steven S. & Zumdahl, Susan A. (2008). "No lead pencils". Chemistry. Belmont, CA: Cengage Learning. p. 343. ISBN 978-0-547-12532-9.

Roald Dahl used only pencils with yellow casing to write his books. He had 6 sharpened pencils ready at the beginning of each day and only when all 6 pencils became unusable did he resharpen them. [81] Golf pencils are usually short (a common length is 9cm or 3.5in) and very cheap. They are also known as library pencils, as many libraries offer them as disposable, leak-proof – if it doesn't have ink, it can't leak – writing instruments. One effect of this was that "during World War II rotary pencil sharpeners were outlawed in Britain because they wasted so much scarce lead and wood, and pencils had to be sharpened in the more conservative manner – with knives." [30] The most common pencil casing is thin wood, usually hexagonal in section but sometimes cylindrical or triangular, permanently bonded to the core. Casings may be of other materials, such as plastic or paper. To use the pencil, the casing must be carved or peeled off to expose the working end of the core as a sharp point. Mechanical pencils have more elaborate casings which are not bonded to the core; instead, they support separate, mobile pigment cores that can be extended or retracted (usually through the casing's tip) as needed. These casings can be reloaded with new cores (usually graphite) as the previous ones are exhausted.The majority of pencils made in the US are painted yellow. [e] According to Henry Petroski, [74] this tradition began in 1890 when the L. & C. Hardtmuth Company of Austria-Hungary introduced their Koh-I-Noor brand, named after the famous diamond. It was intended to be the world's best and most expensive pencil, as the ends of the pencil was dipped in 14-carat gold, [75] and at a time when most pencils were either painted in dark colours or not at all, the Koh-I-Noor was yellow. Pencil grades vary "depending upon the manufacturer, when the pencils are made, and the source of graphite and clay. One analyst found that graphitic carbon content, for example, to vary from about 30 to about 65 in a variety of different pencils bearing the same designation." Petroski 1990, p. 229 American colonists imported pencils from Europe until after the American Revolution. Benjamin Franklin advertised pencils for sale in his Pennsylvania Gazette in 1729, and George Washington used a three inches (7.5cm) pencil when he surveyed the Ohio Country in 1762. [26] [ bettersourceneeded] William Munroe, a cabinetmaker in Concord, Massachusetts, made the first American wood pencils in 1812. This was not the only pencil-making occurring in Concord. According to Henry Petroski, transcendentalist philosopher Henry David Thoreau discovered how to make a good pencil out of inferior graphite using clay as the binder; this invention was prompted by his father's pencil factory in Concord, which employed graphite found in New Hampshire in 1821 by Charles Dunbar. [7] Definition of Plumbago". Answers.com. Archived from the original on 13 August 2007 . Retrieved 21 April 2007. Lakeland's Mining Heritage". cumbria-industries.org.uk. Archived from the original on 15 March 2008 . Retrieved 27 March 2008.

Graphite Grading Scales Explained". 8 November 2014. Archived from the original on 6 February 2017 . Retrieved 5 February 2017.Gyaat:The weapon we use from adolescence". www.gyaat.com. Archived from the original on 23 November 2015 . Retrieved 23 November 2015. Derwent Graphic". Pencils.co.uk. Archived from the original on 19 June 2009 . Retrieved 23 July 2009. The lead of the pencil is a mix of finely ground graphite and clay powders. Before the two substances are mixed, they are separately cleaned of foreign matter and dried in a manner that creates large square cakes. Once the cakes have fully dried, the graphite and the clay squares are mixed together using water. The amount of clay content added to the graphite depends on the intended pencil hardness (lower proportions of clay makes the core softer), [57] and the amount of time spent on grinding the mixture determines the quality of the lead. The mixture is then shaped into long spaghetti-like strings, straightened, dried, cut, and then tempered in a kiln. The resulting strings are dipped in oil or molten wax, which seeps into the tiny holes of the material and allows for the smooth writing ability of the pencil. A juniper or incense-cedar plank with several long parallel grooves is cut to fashion a "slat," and the graphite/clay strings are inserted into the grooves. Another grooved plank is glued on top, and the whole assembly is then cut into individual pencils, which are then varnished or painted. Many pencils feature an eraser on the top and so the process is usually still considered incomplete at this point. Each pencil has a shoulder cut on one end of the pencil to allow for a metal ferrule to be secured onto the wood. A rubber plug is then inserted into the ferrule for a functioning eraser on the end of the pencil. [58] Grading and classification Two graphite pencils. Both are labelled "HB", but the numeric label differs between "2" and "2 1⁄ 2". A grading chart ranging from 9B to 9H Manufacturers distinguish their pencils by grading them, but there is no common standard. [62] Two pencils of the same grade but different manufacturers will not necessarily make a mark of identical tone nor have the same hardness. [a] Poe, Janita (1 September 1993). "In World Of Politically Right, Pencils Can Be Wrong Stuff". Chicago Tribune. Archived from the original on 22 February 2014.

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